Structural adhesive compositions

ABSTRACT

Disclosed herein are compositions including (a) a first component comprising (1) an epoxy-adduct that is the reaction product of reactants comprising a first epoxy compound, a polyol, and an anhydride and/or a diacid and (2) a second epoxy compound; (b) rubber particles having a core/shell structure and/or graphenic carbon particles; and (c) a second component that chemically reacts with the first component at ambient or slightly thermal conditions. Also disclosed herein are compositions including (a) an epoxy-capped flexibilizer; (b) a heat-activated latent curing agent; and optionally (c) rubber particles having a core/shell structure and/or graphenic carbon particles; (d) an epoxy/CTBN adduct; and/or (e) an epoxy/dimer acid adduct. The heat-activated latent curing agent may include at least one reaction product of reactants including an epoxy compound and an amine and/or an alkaloid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of Ser. No. 13/918,021, filed Jun. 14, 2013 andentitled “Structural Adhesive Compositions”, which is acontinuation-in-part of U.S. patent application Ser. No. 13/315,518,filed Dec. 9, 2011, and entitled “Structural Adhesive Compositions,”which is a continuation-in-part of U.S. patent application Ser. No.12/949,878, filed Nov. 19, 2010 and entitled “Structural AdhesiveCompositions”.

FIELD OF THE INVENTION

The present invention relates to structural adhesive compositions andmore particularly to 1K and 2K structural adhesive compositions.

BACKGROUND INFORMATION

Structural adhesives are utilized in a wide variety of applications tobond together two or more substrate materials. For example, structuraladhesives may be used for binding together wind turbine blades orbinding together automotive structural components.

The present invention is directed towards one-component (1K) andtwo-component (2K) adhesive compositions that provide sufficient bondstrength, are easy to apply, and, where applicable, have sufficientlylong pot lives for use in bonding together substrate materials.

SUMMARY OF THE INVENTION

In an embodiment, disclosed is a composition comprising (a) anepoxy-capped flexibilizer; and (b) a heat-activated latent curing agentcomprising a reaction product of reactants comprising (i) an epoxycompound, and (ii) an amine and/or an alkaloid.

Also disclosed is method of adhering articles comprising (a) applyingthe composition to at least one of the articles; and (b) heating thecomposition at a temperature of less than 140° C. for a time of lessthan 15 minutes to cure the composition and thereby adhering thearticles together.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a perspective view of a Teflon template assembly forevaluating tensile properties of structural adhesives according to anexemplary embodiment of the present invention.

DETAILED DESCRIPTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims, are to be understoodas being modified in all instances by the term “about”. Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

In this application and the appended claims, the articles “a,” “an,” and“the” include plural referents unless expressly and unequivocallylimited to one referent. For examples, “a” reaction product, “an” epoxycompound, “an” amine, and “an” alkaloid means one or more reactionproducts, epoxy compounds, amines, and alkaloids, respectively.

As noted above, in general, the present invention discloses 1K(“One-Component) and 2K (“Two-Component”) structural adhesivecompositions that are used to bond together two substrate materials fora wide variety of potential applications in which the bond between thesubstrate materials provides particular mechanical properties related toelongation, tensile strength, lap shear strength, T-peel strength,modulus, or impact peel strength. The structural adhesive is applied toeither one or both of the materials being bonded. The pieces are alignedand pressure and spacers may be added to control bond thickness. For 2Kadhesives, the curing begins upon the mixing together of the componentsat ambient or slightly thermal temperatures. By contrast for 1Kadhesives, the adhesive is cured using an external source such as anoven (or other thermal means) or through the use of actinic radiation(UV light, etc.).

Suitable substrate materials that may be bonded by the structuraladhesive compositions include, but are not limited to, materials suchas, metals or metal alloys, natural materials such as wood, polymericmaterials such as hard plastics, or composite materials. The structuraladhesives of the present invention are particularly suitable for use invarious automotive applications and for use in wind turbine technology.

As noted above, the structural adhesive compositions of the presentinvention are suitable for use in bonding the two half shells of windturbine blades. In this application, for a 2K adhesive, the mixedadhesive composition is applied along the edges of one or both of thehalf shells of the wind turbine blades. The half shells are then pressedtogether and the 2K adhesive is allowed to cure for a number of hours atambient or slightly thermal conditions. A thermal blanket (at about 70°C.) may be applied to the half shells to aid in the curing process. Bycontrast, for 1K adhesives, as opposed to a system in which thecomponents substantially cure upon mixing, an oven or actinic radiationsource is used to complete the curing process.

The half shells, or other components of wind turbine blades, may beformed from metals such as aluminum, metal alloys such as steel, woodssuch balsa wood, polymeric materials such as hard plastics, or compositematerials such as fiber reinforced plastics. In one embodiment, the halfshells are formed from fiberglass composites or carbon fiber composites.

The 2K structural adhesives of the present invention are formed from twochemical components, namely, a first component and a second componentwhich are mixed just prior to application. The first component (i.e., anepoxy component), in certain embodiments, comprises an epoxy-adduct andanother epoxy compound, or second epoxy compound. The second component,in certain embodiments, comprises a curing component that reacts withthe first component to form a bond that provides the substrates to whichit is applied with desirable bonding characteristics. In certainembodiments, the curing component is an amine compound, although othercuring components such as sulfide curing components may alternatively beutilized.

The equivalent ratio of amine to epoxy in the adhesive composition mayvary from about 0.5:1 to about 1.5:1, such as from 1.0:1 to 1.25:1. Incertain embodiments, the equivalent ratio of amine to epoxy is slightlyabove 1:1. As described herein, the equivalents of epoxy used incalculating the equivalent ratio of epoxy are based on the epoxyequivalent weight of the first component, and the equivalents of amineused in calculating the equivalent ratio of amine are based on the aminehydrogen equivalent weight (AHEW) of the second component.

In one embodiment, the epoxy-adduct is formed as the reaction product ofreactants comprising a first epoxy compound, a polyol, and an anhydride.

In another embodiment, the epoxy-adduct is formed as the reactionproduct of reactants comprising a first epoxy compound, a polyol, and adiacid.

In still another embodiment, the epoxy-adduct is formed as the reactionproduct of reactants comprising a first epoxy compound, a polyol, ananhydride, and a diacid.

In these embodiments, the epoxy-adduct comprises from 3 to 50 weightpercent such as from 3 to 25 weight percent of the first component,while the second epoxy compound comprises from 50 to 97 weight percentsuch as from 75 to 97 weight percent of the first component.

Useful first epoxy compounds that can be used to form the epoxy-adductinclude polyepoxides. Suitable polyepoxides include polyglycidyl ethersof Bisphenol A, such as Epon® 828 and 1001 epoxy resins, and Bisphenol Fdiepoxides, such as Epon® 862, which are commercially available fromHexion Specialty Chemicals, Inc. Other useful polyepoxides includepolyglycidyl ethers of polyhydric alcohols, polyglycidyl esters ofpolycarboxylic acids, polyepoxides that are derived from the epoxidationof an olefinically unsaturated alicyclic compound, polyepoxidescontaining oxyalkylene groups in the epoxy molecule, and epoxy novolacresins. Still other non-limiting first epoxy compounds includeepoxidized Bisphenol A novolacs, epoxidized phenolic novolacs,epoxidized cresylic novolac, and triglycidyl p-aminophenolbismaleiimide.

Useful polyols that may be used to form the epoxy-adduct include diols,triols, tetraols and higher functional polyols. The polyols can be basedon a polyether chain derived from ethylene glycol, propylene glycol,butylenes glycol, hexylene glycol and the like and mixtures thereof. Thepolyol can also be based on a polyester chain derived from ring openingpolymerization of caprolactone. Suitable polyols may also includepolyether polyol, polyurethane polyol, polyurea polyol, acrylic polyol,polyester polyol, polybutadiene polyol, hydrogenated polybutadienepolyol, polycarbonate polyols, polysiloxane polyol, and combinationsthereof. Polyamines corresponding to polyols can also be used, and inthis case, amides instead of carboxylic esters will be formed with acidsand anhydrides.

Suitable diols that may be utilized to form the epoxy-adduct are diolshaving a hydroxyl equivalent weight of between 30 and 1000. Exemplarydiols having a hydroxyl equivalent weight from 30 to 1000 include diolssold under the trade name Terathane®, including Terathane® 250,available from Invista. Other exemplary diols having a hydroxylequivalent weight from 30 to 1000 include ethylene glycol and itspolyether diols, propylene glycol and its polyether diols, butylenesglycol and its polyether diols, hexylene glycols and its polyetherdiols, polyester diols synthesized by ring opening polymerization ofcaprolactone, and urethane diols synthesized by reaction of cycliccarbonates with diamines. Combination of these diols and polyether diolsderived from combination various diols described above could also beused. Dimer diols may also be used including those sold under tradenames Pripol® and Solvermol™ available from Cognis Corporation.

Polytetrahydrofuran-based polyols sold under the trade name Terathane®,including Terathane® 650, available from Invista, may be used. Inaddition, polyols based on dimer diols sold under the trade namesPripol® and Empol®, available from Cognis Corporation, or bio-basedpolyols, such as the tetrafunctional polyol Agrol 4.0, available fromBioBased Technologies, may also be utilized.

Useful anhydride compounds to functionalize the polyol with acid groupsinclude hexahydrophthalic anhydride and its derivatives (e.g. methylhexahydrophthalic anhydride); phthalic anhydride and its derivatives(e.g. methyl phthalic anhydride); maleic anhydride; succinic anhydride;trimelletic anhydride; pyromelletic dianhydride (PMDA); 3,3′,4,4′-oxydiphthalic dianhydride (ODPA); 3,3′,4,4′-benzopheronetetracarboxylic dianhydride (BTDA); and 4,4′-diphthalic(hexamfluoroisopropylidene) anhydride (6FDA). Useful diacid compounds tofunctionalize the polyol with acid groups include phthalic acid and itsderivates (e.g. methyl phthalic acid), hexahydrophthalic acid and itsderivatives (e.g. methyl hexahydrophthalic acid), maleic acid, succinicacid, adipic acid, etc. Any diacid and anhydride can be used; however,anhydrides are preferred.

In one embodiment, the polyol comprises a diol, the anhydride and/ordiacid comprises a monoanhydride or a diacid, and the first epoxycompound comprises a diepoxy compound, wherein the mole ratio of diol,monoanhydride (or diacid), and diepoxy compounds in the epoxy-adduct mayvary from 0.5:0.8:1.0 to 0.5:1.0:6.0.

In another embodiment, the polyol comprises a diol, the anhydride and/ordiacid comprises a monoanhydride or a diacid, and the first epoxycompound comprises a diepoxy compound, wherein the mole ratio of diol,monoanhydride (or a diacid), and diepoxy compounds in the epoxy-adductmay vary from 0.5:0.8:0.6 to 0.5:1.0:6.0.

In another embodiment, the second epoxy compound of the first componentis a diepoxide compound that has an epoxy equivalent weight of betweenabout 150 and about 1000. Suitable diepoxides having an epoxy equivalentweight of between about 150 and about 1000 include polyglycidyl ethersof Bisphenol A, such as Epon® 828 and 1001 epoxy resins, and Bisphenol Fdiepoxides, such as Epon® 862, which are commercially available fromHexion Specialty Chemicals, Inc.

In another embodiment, the second epoxy compound of the first componentis a diepoxide compound or a higher functional epoxides (collectively, a“polyepoxide”), including polyglycidyl ethers of polyhydric alcohols,polyglycidyl esters of polycarboxylic acids, polyepoxides that arederived from the epoxidation of an olefinically unsaturated alicycliccompound, polyepoxides containing oxyalkylene groups in the epoxymolecule, and epoxy novolac resins.

Still other non-limiting second epoxy compounds include epoxidizedBisphenol A novolacs, epoxidized phenolic novolacs, epoxidized cresylicnovolac, and triglycidyl p-aminophenol bismaleiimide.

In another embodiment, the second epoxy compound of the first componentcomprises an epoxy-dimer acid adduct. The epoxy-dimer acid adduct may beformed as the reaction product of reactants comprising a diepoxidecompound (such as a Bisphenol A epoxy compound) and a dimer acid (suchas a C₃₆ dimer acid).

In another embodiment, the second epoxy compound of the first componentcomprises a carboxyl-terminated butadiene-acrylonitrile copolymermodified epoxy compound.

Useful amine compounds that may be used include primary amines,secondary amines, tertiary amines, and combinations thereof. Usefulamine compounds that can be used include diamines, triamines,tetramines, and higher functional polyamines.

Suitable primary amines include alkyl diamines such as1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane,neopentyldiamine, 1,8-diaminooctane, 1,10-diaminodecane,1,-12-diaminododecane and the like; 1,5-diamino-3-oxapentane,diethylene-triamine, triethylenetetramine, tetraethylenepentamine andthe like; cycloaliphatic diamines such as1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane,1,4-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane and thelike; aromatic alkyl diamines such as 1,3-bis(aminomethyl)benzene(m-xylene diamine) and 1,4-bis(aminomethyl)benzene (p-xylenediamine) andtheir reaction products with epichlorohydrin such as Gaskamine 328 andthe like; amine-terminated polyethyleneglycol such as HuntsmanCorporation Jeffamine ED series and amine-terminated polypropyleneglycol such as Huntsman Corporation Jeffamine D series; andamine-terminated polytetrahydrofurane such as Huntsman Jeffamine EDRseries. Primary amines having a functionality higher than 2 include, forexample, the Jeffamine T series, available from Huntsman Corporation,which are amine-terminated propoxylated trimethylolpropane or glyceroland aminated propoxylated pentaerythritols.

Still other amines that may be utilized include isophorone diamine,methenediamine, 4,8-diamino-tricyclio[5.2.1.0]decane andN-aminoethylpiperazine.

In certain embodiments, the amine compounds comprisetriethylenetetramine (TETA), isophorone diamine, 1,3bis(aminomethyl)cyclohexane, and polypropylene oxide-basedpolyetheramines.

In certain embodiments, the polypropylene oxide-based polyetheraminescomprise the Jeffamine series products available from Huntsman Chemicalof Houston, Tex. Jeffamine series products are polyetheraminescharacterized by repeating oxypropylene units in their respectivestructures.

One exemplary class of Jeffamine products, the so-called “Jeffamine D”series products, are amine terminated PPGs (propylene glycols) with thefollowing representative structure (Formula (I)):

wherein x is 2 to 70.

In certain embodiments, Jeffamine D-230 is one D series product that isused. Jeffamine D-230 has an average molecular weight of about 230(wherein x is 2.5) and an amine hydrogen equivalent weight (AHEW) ofabout 60. Other exemplary Jeffamine D series products that may be usedaccording to Formula (I) include those wherein x is from 2.5 to 68.

Another series of polypropylene oxide-based polyetheramines that areused are predominantly tetrafunctional, primary amines with a numberaverage molecular weight from 200 to 2000, and more preferably from 600to 700, and having an AHEW of greater than 60, and more preferably from70 to 90. Jeffamine XTJ-616 is one such polypropylene oxide-basedpolyetheramines that may be utilized in the present invention. JeffamineXTJ-616 has a number average molecular weight of about 660 and an AHEWof 83.

Higher AHEW amine compounds, such as Jeffamine XTJ-616 and JeffamineD-230, may be particularly useful in 2K adhesive composition wherein alonger pot life is desired. Conventional tetramines, such astriethylenetetramine, with lower AHEWS have substantially shorter potlives by comparison. This present invention thus provides a way tomanipulate pot life with tetrafunctional amines such as JeffamineXTJ-616.

In still another embodiment, reinforcement fillers may be added to theadhesive composition as a part of the first component or as a part ofthe second component, or both.

Useful reinforcement fillers that may be introduced to the adhesivecomposition to provide improved mechanical properties include fibrousmaterials such as fiberglass, fibrous titanium dioxide, whisker typecalcium carbonate (aragonite), and carbon fiber (which includes graphiteand carbon nanotubes). In addition, fiber glass ground to 5 microns orwider and to 50 microns or longer may also provide additional tensilestrength. More preferably, fiber glass ground to 5 microns or wider andto 100-300 microns in length is utilized. Preferably, such reinforcementfillers, if utilized, comprise from 0.5 to 25 weight percent of theadhesive composition.

In still another embodiment, fillers, thixotropes, colorants, tints andother materials may be added to the first or second component of theadhesive composition.

Useful thixotropes that may be used include untreated fumed silica andtreated fumed silica, Castor wax, clay, and organo clay. In addition,fibers such as synthetic fibers like Aramid® fiber and Kevlar® fiber,acrylic fibers, and engineered cellulose fiber may also be utilized.

Useful colorants or tints may include red iron pigment, titaniumdioxide, calcium carbonate, and phthalocyanine blue.

Useful fillers that may be used in conjunction with thixotropes mayinclude inorganic fillers such as inorganic clay or silica.

In still another embodiment, if needed, a catalyst may be introduced tothe adhesive composition, preferably as a part of the second component,to promote the reaction of the epoxide groups of first component andamine groups of the second component.

Useful catalysts that may be introduced to the adhesive compositioninclude Ancamide® products available from Air Products and productsmarketed as “Accelerators” available from the Huntsman Corporation. Oneexemplary catalyst is piperazine-base Accelerator 399 (AHEW: 145)available from the Huntsman Corporation. When utilized, such catalystscomprise between 0 and about 10 percent by weight of the total adhesivecomposition.

In addition, a catalytic effect may be expected from the reactionproduct of epichlorohydrin from the first component and the aminecompound from the second component in an equivalent ratio of 1:1. Anexample of such a product is Tetrad® and Tetrad®C available fromMitsubishi Gas Chemical Corporation.

In certain embodiments, rubber particles having a core/shell structuremay be included in the 2K structural adhesive formulation.

Suitable core-shell rubber particles are comprised of butadiene rubber;however, other synthetic rubbers could be employed; such asstyrene-butadiene and acrylonitrile-butadiene and the like. The type ofsynthetic rubber and the rubber concentration should not be limited aslong as the particle size falls under the specified range as illustratedbelow.

In certain embodiments, the average particle size of the rubberparticles may be from about 0.02 to 500 microns (20 nm to 500,000 nm).

In certain embodiments, the core/shell rubber particles are included inan epoxy carrier resin for introduction to the 2K adhesive composition.Suitable finely dispersed core-shell rubber particles in an averageparticle size ranging from 50 nm to 250 nm are master-batched in epoxyresin such as aromatic epoxides, phenolic novolac epoxy resin, bisphenolA and bisphenol F diepoxide and aliphatic epoxides, which includecyclo-aliphatic epoxides at concentration ranging from 20 to 40 weightpercent. Suitable epoxy resins may also includes a mixture of epoxyresins.

Exemplary non-limiting commercial core/shell rubber particle productsusing poly(butadiene) rubber particles having an average particle sizeof 100 nm that may be utilized in the 2K adhesive composition includesKane Ace MX 136 (a core-shell poly(butadiene) rubber dispersion (25%) inbisphenol F), Kane Ace MX 153 (a core-shell poly(butadiene) rubberdispersion (33%) in Epon® 828), Kane Ace MX 257 (a core-shellpoly(butadiene) rubber dispersion (37%) in bisphenol A), and Kane Ace MX267 (a core-shell poly(butadiene) rubber dispersion (37%) in bisphenolF), each available from Kaneka Tex. Corporation.

Exemplary non-limiting commercial core/shell rubber particle productsusing styrene-butadiene rubber particles having an average particle sizeof 100 nm that may be utilized in the 2K adhesive composition includesKane Ace MX 113 (a core-shell styrene-butadiene rubber dispersion (33%)in low viscosity bisphenol A), Kane Ace MX 125 (a core-shellstyrene-butadiene rubber dispersion (25%) in bisphenol A), Kane Ace MX215 (a core-shell styrene-butadiene rubber dispersion (25%) in DEN-438phenolic novolac epoxy), and Kane Ace MX 416 (a core-shellstyrene-butadiene rubber dispersion (25%) in MY-721 multi-functionalepoxy), Kane Ace MX 451 (a core-shell styrene-butadiene rubberdispersion (25%) in MY-0510 multi-functional epoxy), Kane Ace MX 551 (acore-shell styrene-butadiene rubber dispersion (25%) in Synasia 21Cyclo-aliphatic Epoxy), Kane Ace MX 715 (a core-shell styrene-butadienerubber dispersion (25%) in polypropylene glycol (MW 400)), eachavailable from Kaneka Tex. Corporation.

In certain embodiments, the amount of core/shell rubber particlesincluded in the 2K adhesive formulation is from 0.1 to 10 weightpercent, such as from 0.5 to 5 weight percent, based on the total weightof the 2K coating composition.

In still other embodiments, graphenic carbon particles may be includedin the 2K structural adhesive formulation.

Graphene, as defined herein, is an allotrope of carbon, whose structureis one-atom-thick planar sheets of sp²-bonded carbon atoms that aredensely packed in a honeycomb crystal lattice. Graphene is stable,chemically inert and mechanically robust under ambient conditions. Asused herein, the term “graphenic carbon particles” means carbonparticles having structures comprising one or more layers ofone-atom-thick planar sheets of sp²-bonded carbon atoms that are denselypacked in a honeycomb crystal lattice. As such, the term “grapheniccarbon particles” includes one layer thick sheets (i.e. graphene) andmultilayer thick sheets. The average number of stacked layers may beless than 100, for example, less than 50. In certain embodiments, theaverage number of stacked layers is 30 or less. The graphenic carbonparticles may be substantially flat, however, at least a portion of theplanar sheets may be substantially curved, curled or buckled. Theparticles typically do not have a spheroidal or equiaxed morphology.

In certain embodiments, the graphenic carbon particles utilized in thepresent invention have a thickness, measured in a directionperpendicular to the carbon atom layers, of no more than 10 nanometers,such as no more than 5 nanometers, or, in certain embodiments, no morethan 3 or 1 nanometers. In certain embodiments, the graphenic carbonparticles may be from 1 atom layer to 10, 20 or 30 atom layers thick, ormore. The graphenic carbon particles may be provided in the form ofultrathin flakes, platelets or sheets having relatively high aspectratios of greater than 3:1, such as greater than 10:1.

In certain embodiments, graphenic carbon particles are roll-milled in anepoxy carrier resin, such as Epon® 828, for introduction to the 2Kadhesive composition. In one exemplary embodiment, a master-batch ofgraphenic carbon particles/added epoxy resin is formed by milling thegraphenic carbon particles into the epoxy resin at 10 weight percent orhigher concentration. A dispersing method includes typical pigment grindmills such as three-roll mill, Eiger mill, Netsch/Premier mill and thelike.

One exemplary graphenic carbon particle material that may be used in the2K adhesive formulation is XG Sciences Graphene Grade C, which has asurface area of 750 m²/g, an average thickness about 2 nano-meters, andan average diameter less than 2 microns.

In certain embodiments, the amount of graphenic carbon particlesincluded in the 2K adhesive formulation is sufficient to provideincreased tensile modulus while maintaining a glass transitiontemperature as compared with formulations not including the grapheniccarbon particles.

In certain embodiments, the amount of graphenic carbon particlesincluded in the 2K adhesive formulation is from about 0.5 to 25 weightpercent based on the total weight of the 2K coating composition.

As also noted above, in certain embodiments, the 1K structural adhesivesof the present invention comprise: (a) an epoxy-capped flexibilizer; and(b) a heat-activated latent curing agent. In certain other embodiments,the 1K structural adhesives may further comprise one or more of thefollowing components: (c) an epoxy/CTBN (carboxy-terminated butadieneacrylonitrile polymer) adduct; (d) an epoxy/dimer acid adduct; (e)rubber particles having a core/shell structure; and (f) graphenic carbonparticles. Each component (a)-(e) is described further below.

In certain embodiments, the (a) epoxy-capped flexibilizer is formed asthe reaction product of reactants comprising a first epoxy compound, apolyol, and an anhydride and/or a diacid (i.e. an anhydride, a diacid,or both an anhydride and a diacid may be part of the reaction product).

Useful epoxy compounds that can be used include polyepoxides. Suitablepolyepoxides include polyglycidyl ethers of Bisphenol A, such as Epon®828 and 1001 epoxy resins, and Bisphenol F diepoxides, such as Epon®862, which are commercially available from Hexion Specialty Chemicals,Inc. Other useful polyepoxides include polyglycidyl ethers of polyhydricalcohols, polyglycidyl esters of polycarboxylic acids, polyepoxides thatare derived from the epoxidation of an olefinically unsaturatedalicyclic compound, polyepoxides containing oxyalkylene groups in theepoxy molecule, and epoxy novolac resins. Still other non-limiting firstepoxy compounds include epoxidized Bisphenol A novolacs, epoxidizedphenolic novolacs, epoxidized cresylic novolac, and triglycidylp-aminophenol bismaleiimide.

Useful polyols that may be used include diols, triols, tetraols andhigher functional polyols. The polyols can be based on a polyether chainderived from ethylene glycol, propylene glycol, butylenes glycol,hexylene glycol and the like and mixtures thereof. The polyol can alsobe based on a polyester chain derived from ring opening polymerizationof caprolactone. Suitable polyols may also include polyether polyol,polyurethane polyol, polyurea polyol, acrylic polyol, polyester polyol,polybutadiene polyol, hydrogenated polybutadiene polyol, polycarbonatepolyols, polysiloxane polyol, and combinations thereof. Polyaminescorresponding to polyols can also be used, and in this case, amidesinstead of carboxylic esters will be formed with acids and anhydrides.

Suitable diols that may be utilized are diols having a hydroxylequivalent weight of between 30 and 1000. Exemplary diols having ahydroxyl equivalent weight from 30 to 1000 include diols sold under thetrade name Terathane®, including Terathane® 250, available from Invista.Other exemplary diols having a hydroxyl equivalent weight from 30 to1000 include ethylene glycol and its polyether diols, propylene glycoland its polyether diols, butylenes glycol and its polyether diols,hexylene glycols and its polyether diols, polyester diols synthesized byring opening polymerization of caprolactone, and urethane diolssynthesized by reaction of cyclic carbonates with diamines. Combinationof these diols and polyether diols derived from combination variousdiols described above could also be used. Dimer diols may also be usedincluding those sold under trade names Pripol® and Solvermol™ availablefrom Cognis Corporation.

Polytetrahydrofuran-based polyols sold under the trade name Terathane®,including Terathane® 650, available from Invista, may be used. Inaddition, polyols based on dimer diols sold under the trade namesPripol® and Empol®, available from Cognis Corporation, or bio-basedpolyols, such as the tetrafunctional polyol Agrol 4.0, available fromBioBased Technologies, may also be utilized.

Useful anhydride compounds to functionalize the polyol with acid groupsinclude hexahydrophthalic anhydride and its derivatives (e.g. methylhexahydrophthalic anhydride); phthalic anhydride and its derivatives(e.g. methyl phthalic anhydride); maleic anhydride; succinic anhydride;trimelletic anhydride; pyromelletic dianyhydrige (PMDA);3,3′,4,4′-oxydiphthalic dianhydride (ODPA); 3,3′,4,4′-benzopheronetetracarboxylic dianhydride (BTDA); and 4,4′-diphthalic(hexamfluoroisopropylidene) anhydride (6FDA). Useful diacid compounds tofunctionalize the polyol with acid groups include phthalic acid and itsderivates (e.g. methyl phthalic acid), hexahydrophthalic acid and itsderivatives (e.g. methyl hexahydrophthalic acid), maleic acid, succinicacid, adipic acid, etc. Any diacid and anhydride can be used; however,anhydrides are preferred.

In one embodiment, the polyol comprises a diol, the anhydride and/ordiacid comprises a monoanhydride or a diacid, and the first epoxycompound comprises a diepoxy compound, wherein the mole ratio of diol,monoanhydride (or diacid), and diepoxy compounds in the epoxy-cappedflexibilizer may vary from 0.5:0.8:1.0 to 0.5:1.0:6.0.

In another embodiment, the polyol comprises a diol, the anhydride and/ordiacid comprises a monoanhydride or a diacid, and the first epoxycompound comprises a diepoxy compound, wherein the mole ratio of diol,monoanhydride (or a diacid), and diepoxy compounds in the epoxy-cappedflexibilizer may vary from 0.5:0.8:0.6 to 0.5:1.0:6.0.

In certain embodiments, the (a) epoxy-capped flexibilizer comprises thereaction product of reactants comprising an epoxy compound, an anhydrideand/or a diacid, and a caprolactone. In certain other embodiments, adiamine and/or a higher functional amine may also be included in thereaction product in addition to the epoxy compound, caprolactone, andthe anhydride and/or a diacid.

Suitable epoxy compounds that may be used to form the epoxy-cappedflexibilizer include epoxy-functional polymers that can be saturated orunsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic orheterocyclic. The epoxy-functional polymers can have pendant or terminalhydroxyl groups, if desired. They can contain substituents such ashalogen, hydroxyl, and ether groups. A useful class of these materialsincludes polyepoxides comprising epoxy polyethers obtained by reactingan epihalohydrin (such as epichlorohydrin or epibromohydrin) with a di-or polyhydric alcohol in the presence of an alkali. Suitable polyhydricalcohols include polyphenols such as resorcinol; catechol; hydroquinone;bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Frequently used polyepoxides include polyglycidyl ethers of Bisphenol A,such as Epon® 828 epoxy resin which is commercially available fromHexion Specialty Chemicals, Inc and having a number average molecularweight of about 400 and an epoxy equivalent weight of about 185-192.Other useful polyepoxides include polyglycidyl ethers of otherpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, epoxy novolac resins, and polyepoxidesthat are partially defunctionalized by carboxylic acids, alcohol, water,phenols, mercaptans or other active hydrogen-containing compounds togive hydroxyl-containing polymers.

Useful anhydride compounds that may be utilized includehexahydrophthalic anhydride and its derivatives (e.g. methylhexahydrophthalic anhydride); phthalic anhydride and its derivatives(e.g. methyl phthalic anhydride); maleic anhydride; succinic anhydride;trimelletic anhydride; pyromelletic dianyhydrige (PMDA);3,3′,4,4′-oxydiphthalic dianhydride (ODPA); 3,3′,4,4′-benzopheronetetracarboxylic dianhydride (BTDA); and 4,4′-diphthalic(hexamfluoroisopropylidene) anhydride (6FDA). Useful diacid compounds tofunctionalize the polyol with acid groups include phthalic acid and itsderivates (e.g. methyl phthalic acid), hexahydrophthalic acid and itsderivatives (e.g. methyl hexahydrophthalic acid), maleic acid, succinicacid, adipic acid, etc. Any diacid and anhydride can be used; however,anhydrides are preferred.

Useful caprolactones that can be used include caprolactone monomer,methyl, ethyl, and propyl substituted caprolactone monomer, andpolyester diols derived from caprolactone monomer. Exemplary polyesterdiols having a molecular weight from about 400 to 8000 include diolssold under the trade name CAPA®, including CAPA® 2085, available fromPerstorp.

Useful diamine or higher functional amine compounds that can be used toform the epoxy-capped flexibilizer include primary amines, secondaryamines, tertiary amines, and combinations thereof. Useful aminecompounds that can be used include diamines, triamines, tetramines, andhigher functional polyamines.

Suitable primary diamines or higher functional amines that may be usedinclude alkyl diamines such as 1,2-diaminoethane, 1,3-diaminopropane,1,4-diaminobutane, neopentyldiamine, 1,8-diaminooctane,1,10-diaminodecane, 1,-12-diaminododecane and the like;1,5-diamino-3-oxapentane, diethylene-triamine, tri ethylenetetramine,tetraethylenepentamine and the like; cycloaliphatic diamines such as1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane,1,4-bis(aminomethyl)cyclohexane, bis(aminomethyl)norbornane and thelike; aromatic alkyl diamines such as 1,3-bis(aminomethyl)benzene(m-xylene diamine) and 1,4-bis(aminomethyl)benzene (p-xylenediamine) andtheir reaction products with epichlorohydrin such as Gaskamine 328 andthe like; amine-terminated polyethyleneglycol such as HuntsmanCorporation Jeffamine ED series and amine-terminated polypropyleneglycol such as Huntsman Corporation Jeffamine D series; andamine-terminated polytetrahydrofurane such as Huntsman Jeffamine EDRseries. Primary amines having a functionality higher than 2 include, forexample, the Jeffamine T series, available from Huntsman Corporation,which are amine-terminated propoxylated trimethylolpropane or glyceroland aminated propoxylated pentaerythritols.

In certain embodiments, the polypropylene oxide-based polyetheraminescomprise the Jeffamine series products available from Huntsman Chemicalof Houston, Tex. Jeffamine series products are polyetheraminescharacterized by repeating oxypropylene units in their respectivestructures.

One exemplary class of Jeffamine products, the so-called “Jeffamine D”series products, are amine terminated PPGs (propylene glycols) with thefollowing representative structure (Formula (I)):

wherein x is 2 to 70.

In one embodiment, the caprolactone comprises a carprolactone monomer,the anhydride and/or diacid comprises a monoanhydride or a diacid, andthe first epoxy compound comprises a diepoxy compound, wherein the moleratio of caprolactone monomer, monoanhydride (or diacid), and diepoxycompounds in the epoxy-capped flexibilizer may vary from 0.5:0.8:1.0 to0.5:1.0:6.0.

In one embodiment, the caprolactone comprises a carprolactone monomer,the anhydride and/or diacid comprises a monoanhydride or a diacid, andthe first epoxy compound comprises a diepoxy compound, wherein the moleratio of caprolactone monomer, monoanhydride (or diacid), and diepoxycompounds in the epoxy-capped flexibilizer may vary from 0.5:0.8:0.6 to0.5:1.0:6.0.

In one embodiment, the caprolactone comprises a carprolactone monomer,the anhydride and/or diacid comprises a monoanhydride or a diacid, thediamine or higher functional amine comprises a diamine, and the firstepoxy compound comprises a diepoxy compound, wherein the mole ratio ofcaprolactone monomer, monoanhydride (or diacid), diamine and diepoxycompounds in the epoxy-capped flexibilizer may vary from 2:1: 2:2 to3:1:3:3.

In certain embodiments, the (a) epoxy-capped flexibilizer comprises thereaction product of reactants comprising an epoxy compound and a primaryor secondary polyether amine.

Suitable epoxy compounds that may be used to form the epoxy-cappedflexibilizer include epoxy-functional polymers that can be saturated orunsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic orheterocyclic. The epoxy-functional polymers can have pendant or terminalhydroxyl groups, if desired. They can contain substituents such ashalogen, hydroxyl, and ether groups. A useful class of these materialsincludes polyepoxides comprising epoxy polyethers obtained by reactingan epihalohydrin (such as epichlorohydrin or epibromohydrin) with a di-or polyhydric alcohol in the presence of an alkali. Suitable polyhydricalcohols include polyphenols such as resorcinol; catechol; hydroquinone;bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Frequently used polyepoxides include polyglycidyl ethers of Bisphenol A,such as Epon® 828 epoxy resin which is commercially available fromHexion Specialty Chemicals, Inc and having a number average molecularweight of about 400 and an epoxy equivalent weight of about 185-192.Other useful polyepoxides include polyglycidyl ethers of otherpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, epoxy novolac resins, and polyepoxidesthat are partially defunctionalized by carboxylic acids, alcohol, water,phenols, mercaptans or other active hydrogen-containing compounds togive hydroxyl-containing polymers.

Useful primary and secondary polyether amine compounds that can be usedto form the epoxy-capped flexibilizer include amine-terminatedpolyethyleneglycol such as Huntsman Corporation Jeffamine ED series andamine-terminated polypropylene glycol such as Huntsman CorporationJeffamine D series; and amine-terminated polytetrahydrofurane such asHuntsman Jeffamine EDR series. Primary amines having a functionalityhigher than 2 include, for example, the Jeffamine T series, availablefrom Huntsman Corporation, which are amine-terminated propoxylatedtrimethylolpropane or glycerol and aminated propoxylatedpentaerythritols.

In one embodiment, the epoxy compound comprises a diepoxide, and theprimary or secondary polyether amine comprises a difunctional amine,wherein the mole ratio of diepoxide to difunctional amine varies from2:0.2 to 2:1.

In certain embodiments, the 1K structural adhesive may include from 2 to40 weight percent, such as from 10 to 20 weight percent, of (a) theepoxy-capped flexibilizer, based on the total weight of the 1Kstructural adhesive composition, of any of the forms of described above.

In still other related embodiments, the (a) the epoxy-cappedflexibilizer may comprise a mixture of any two or more of theepoxy-capped flexibilizers described above, wherein the total weightpercent of the mixture of the two or more of the epoxy-cappedflexibilizers comprises from 2 to 40 weight percent, such as from 10 to20 weight percent, based on the total weight of the 1K structuraladhesive composition.

In certain embodiments, the (b) heat-activated latent curing agent thatmay be used include guanidines, substituted guanidines, substitutedureas, melamine resins, guanamine derivatives, cyclic tertiary amines,aromatic amines and/or mixtures thereof. The hardeners may be involvedstoichiometrically in the hardening reaction; they may, however, also becatalytically active. Examples of substituted guanidines aremethylguanidine, dimethylguanidine, trimethylguanidine,tetra-methylguani dine, methylisobiguanidine, dimethyli sobiguanidine,tetramethylisobiguanidine, hexamethyli sobiguanidine, heptamethylisobiguanidine and, more especially, cyanoguanidine (dicyandiamide).Representatives of suitable guanamine derivatives which may be mentionedare alkylated benzoguanamine resins, benzoguanamine resins ormethoxymethylethoxymethylbenzoguanamine. In addition,catalytically-active substituted ureas may also be used. Suitablecatalytically-active substituted ureas includep-chlorophenyl-N,N-dimethylurea, 3-phenyl-1,1-dimethylurea (fenuron) or3,4-dichlorophenyl-N,N-dimethylurea.

In certain other embodiments, the (b) heat-activated latent curing agentalso or alternatively comprises dicyandiamide and3,4-dichlorophenyl-N,N-dimethylurea (also known as Diuron).

In certain embodiments, the 1K structural adhesive may include from 3 to25 weight percent, such as from 5 to 10 weight percent, of (b) theheat-activated latent curing agent, based on the total weight of the 1Kstructural adhesive composition.

In certain embodiments, the (b) heat-activated latent curing agent thatmay be used may comprise a reaction product of reactants comprising (i)an epoxy compound, and (ii) an amine and/or an alkaloid. In certainembodiments, the (b) heat-activated latent curing agent that may be usedmay comprise a reaction product of reactants comprising (i) an epoxycompound and (ii) an amine. In certain embodiments, the (b)heat-activated latent curing agent may further comprise a reactionproduct of reactants comprising (i) an epoxy compound and (ii) analkaloid.

In certain embodiments, the molar ratio of the epoxy compound to theamine in the heat-activated latent curing agent may be between 1:2 to8:9, such as between 2:3 to 6:7, such as 4:5. In certain embodiments,the molar ratio of the epoxy compound to the alkaloid in theheat-activated latent curing agent may be between 1:1 to 3:1, such as2:1.

Useful epoxy compounds that may be used to form the reaction productcomprising the heat-activated latent curing catalyst include a diepoxideor a higher functional epoxide (collectively, a “polyepoxide”). Suitablepolyepoxides include polyglycidyl ethers of Bisphenol A, such as Epon®828 and 1001 epoxy resins, and Bisphenol F diepoxides, such as Epon®862, which are commercially available from Hexion Specialty Chemicals,Inc. Other useful polyepoxides include polyglycidyl ethers of polyhydricalcohols, polyglycidyl esters of polycarboxylic acids, polyepoxides thatare derived from the epoxidation of an olefinically unsaturatedalicyclic compound, polyepoxides containing oxyalkylene groups in theepoxy molecule, and epoxy novolac resins, and polyepoxides that arepartially defunctionalized by carboxylic acids, alcohol, water, phenols,mercaptans or other active hydrogen-containing compounds to givehydroxyl-containing polymers. Still other non-limiting epoxy compoundsinclude epoxidized Bisphenol A novolacs, epoxidized phenolic novolacs,epoxidized cresylic novolac, and triglycidyl p-aminophenolbismaleiimide.

Other suitable epoxy compounds that may be used to form the reactionproduct comprising the heat-activated latent curing catalyst includeepoxy-functional polymers that can be saturated or unsaturated, cyclicor acyclic, aliphatic, alicyclic, aromatic or heterocyclic. Theepoxy-functional polymers can have pendant or terminal hydroxyl groups,if desired. They can contain substituents such as halogen, hydroxyl, andether groups. A useful class of these materials includes polyepoxidescomprising epoxy polyethers obtained by reacting an epihalohydrin (suchas epichlorohydrin or epibromohydrin) with a di- or polyhydric alcoholin the presence of an alkali. Suitable polyhydric alcohols includepolyphenols such as resorcinol; catechol; hydroquinone;bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Useful amine compounds that may be used to form the reaction productcomprising the heat-activated latent curing catalyst include primaryamines, secondary amines, tertiary amines, and combinations thereof.Useful amine compounds that may be used to form the reaction productcomprising the heat-activated latent curing catalyst include monoamines,diamines, triamines, tetramines, and higher functional polyamines.

Suitable primary amines that may be used to form the reaction comprisingthe heat-activated latent curing catalyst include alkyl diamines such as1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane,neopentyldiamine, 1,8-diaminooctane, 1,10-diaminodecane,1,-12-diaminododecane and the like; 1,5-diamino-3-oxapentane,diethylene-triamine, triethylenetetramine, tetraethylenepentamine andthe like; cycloaliphatic diamines such as1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane,1,4-bis(aminomethyl) cyclohexane, bis(aminomethyl)norbornane and thelike; aromatic alkyl diamines such as 1,3-bis(aminomethyl)benzene(m-xylene diamine) and 1,4-bis(aminomethyl)benzene (_(Th)xylenediamine)and their reaction products with epichlorohydrin such as Gaskamine 328and the like; amine-terminated polyethyleneglycol such as HuntsmanCorporation Jeffamine ED series and amine-terminated polypropyleneglycol such as Huntsman Corporation Jeffamine D series; andamine-terminated polytetrahydrofurane such as Huntsman Jeffamine EDRseries. Primary amines having a functionality higher than 2 include, forexample, the Jeffamine T series, available from Huntsman Corporation,which are amine-terminated propoxylated trimethylolpropane or glyceroland aminated propoxylated pentaerythritols.

Still other amines that may be utilized to form the reaction productcomprising the heat-activated latent curing catalyst include isophoronediamine, methenediamine, 4,8-diamino-tricyclio[5.2.1.0] decane andN-aminoethylpiperazine.

In certain embodiments, the amine compounds that may be used to form thereaction product comprising the heat-activated latent curing catalystcomprise triethylenetetramine (TETA), isophorone diamine, 1,3bis(aminomethyl)cyclohexane, and polypropylene oxide-basedpolyetheramines.

In certain embodiments, the polypropylene oxide-based polyetheraminescomprise the Jeffamine series products available from Huntsman Chemicalof Houston, Tex. Jeffamine series products are polyetheraminescharacterized by repeating oxypropylene units in their respectivestructures.

One exemplary class of Jeffamine products, the so-called “Jeffamine D”series products, are amine terminated PPGs (propylene glycols) with thefollowing representative structure (Formula (I)):

wherein x is 2 to 70.

In certain embodiments, Jeffamine D-230 is one D series product that isused. Jeffamine D-230 has an average molecular weight of about 230(wherein x is 2.5) and an amine hydrogen equivalent weight (AHEW) ofabout 60. Other exemplary Jeffamine D series products that may be usedaccording to Formula (I) include those wherein x is from 2.5 to 68.

Another series of polypropylene oxide-based polyetheramines that may beused to form the reaction comprising the heat-activated latent curingcatalyst are predominantly tetrafunctional, primary amines with a numberaverage molecular weight from 200 to 2000, and more preferably from 600to 700, and having an AHEW of greater than 60, and more preferably from70 to 90. Jeffamine XTJ-616 is one such polypropylene oxide-basedpolyetheramines that may be utilized in the present invention. JeffamineXTJ-616 has a number average molecular weight of about 660 and an AHEWof 83.

Useful alkaloid compounds that may be used to form the reaction productcomprising the heat-activated latent curing catalyst include azoles,diazoles, triazoles, higher functional azoles, and combinations thereof.Suitable alkaloid compounds include pyrrolidine, tropane, pyrrolizidine,piperidine, quinolizidine, indolizidine, pyridine, isoquinoline,oxazole, isoxazole, thiazole, quinazoline, acridine, quinoline, indole,imidazole, purine, phenethylamine, muscarine, benzylamines, derivativesof these alkaloid compounds, or combinations thereof.

As used herein, the term “cure,” when used with respect to the (b)heat-activated latent curing agent comprising a reaction product ofreactants comprising (i) an epoxy compound, and (ii) an amine and/or analkaloid, means a coating composition that, when applied at 1 mm thickto hot dipped galvanized metal with a bond area of 20 mm×10 mm×0.25 mm,and following heating, has a measured lap shear strength of at least 15MPa when tested at room temperature. In an embodiment, the coatingcomposition comprising the (b) heat activated latent curing agent may becured at a temperature of less than 140° C., such as between 120° C. and140° C., such as 130° C. In an embodiment, the coating compositioncomprising the (b) heat activated-latent curing agent may be cured forless than 20 minutes, such as between 13 and 17 minutes, such as 15minutes.

As noted above, in certain embodiments, the 1K structural adhesivecomposition may include (c) an epoxy/CTBN adduct. In certainembodiments, CTBN liquid polymers undergo addition esterificationreactions with epoxy resins, allowing them to serve as elastomericmodifiers to enhance impact strength, peel strength, and crackresistance.

Suitable epoxy compounds that may be used to form the epoxy/CTBN adductinclude epoxy-functional polymers that can be saturated or unsaturated,cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic. Theepoxy-functional polymers can have pendant or terminal hydroxyl groups,if desired. They can contain substituents such as halogen, hydroxyl, andether groups. A useful class of these materials includes polyepoxidescomprising epoxy polyethers obtained by reacting an epihalohydrin (suchas epichlorohydrin or epibromohydrin) with a di- or polyhydric alcoholin the presence of an alkali. Suitable polyhydric alcohols includepolyphenols such as resorcinol; catechol; hydroquinone;bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Frequently used polyepoxides include polyglycidyl ethers of Bisphenol A,such as Epon® 828 epoxy resin which is commercially available fromHexion Specialty Chemicals, Inc and having a number average molecularweight of about 400 and an epoxy equivalent weight of about 185-192.Other useful polyepoxides include polyglycidyl ethers of otherpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, epoxy novolac resins, and polyepoxidesthat are partially defunctionalized by carboxylic acids, alcohol, water,phenols, mercaptans or other active hydrogen-containing compounds togive hydroxyl-containing polymers.

In certain embodiments, at least a portion, often at least 5 percent byweight, of the polyepoxide has been reacted with a carboxy-terminatedbutadiene acrylonitrile polymer. In certain of these embodiments, thecarboxy-terminated butadiene acrylonitrile polymers have anacrylonitrile content of 10 to 26 percent by weight. Suitable CTBNcompounds having an acrylonitrile content of 10 to 26 percent by weightthat may be used include Hypro 1300X8, Hypro 1300X9, Hypro 1300X13,Hypro 1300X18, and Hypro 1300X31, each available from Emerald SpecialtyPolymers, LLC of Akron, Ohio

In certain other embodiments, the polyepoxide may be reacted with amixture of different carboxy-terminated butadiene acrylonitrilepolymers.

In certain embodiments, the functionality of the CTBN utilized is from1.6 to 2.4, and the epoxy compound is reacted with the CTBN material ina stoichiometric amount to form the epoxy/CTBN adduct.

In certain embodiments, the epoxy/CTBN adduct comprises from about 1 to20 weight percent, such as from 5 to 10 weight percent, of the totalweight of the 1K structural adhesive composition.

As noted above, in certain embodiments, the 1K structural adhesivecomposition may include (d) an epoxy/dimer acid adduct. In certainembodiments, the epoxy/dimer acid adduct may be formed by reacting anepoxy compound with a dimer acid.

Suitable epoxy compounds that may be used to form the epoxy/dimer acidadduct include epoxy-functional polymers that can be saturated orunsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic orheterocyclic. The epoxy-functional polymers can have pendant or terminalhydroxyl groups, if desired. They can contain substituents such ashalogen, hydroxyl, and ether groups. A useful class of these materialsincludes polyepoxides comprising epoxy polyethers obtained by reactingan epihalohydrin (such as epichlorohydrin or epibromohydrin) with a di-or polyhydric alcohol in the presence of an alkali. Suitable polyhydricalcohols include polyphenols such as resorcinol; catechol; hydroquinone;bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Frequently used polyepoxides include polyglycidyl ethers of Bisphenol A,such as Epon® 828 epoxy resin which is commercially available fromHexion Specialty Chemicals, Inc and having a number average molecularweight of about 400 and an epoxy equivalent weight of about 185-192.Other useful polyepoxides include polyglycidyl ethers of otherpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, epoxy novolac resins, and polyepoxidesthat are partially defunctionalized by carboxylic acids, alcohol, water,phenols, mercaptans or other active hydrogen-containing compounds togive hydroxyl-containing polymers.

As defined herein, dimer acids, or dimerized fatty acids, aredicarboxylic acids prepared by dimerizing unsaturated fatty acidsobtained from tall oil, usually on clay catalysts. Dimer acids usuallypredominantly contain a dimer of stearic acid known as C36 dimer acid. Asuitable dimer acid for use in forming the epoxy/dimer acid adduct ofthe present invention may be obtained from Croda, Inc. or from Cognis.

In certain embodiments, the epoxy compounds and dimer acids are reactedin stoichiometric amounts to form the epoxy/dimer acid adduct.

In certain embodiments, the epoxy/dimer acid adduct comprises from about1 to 15 weight percent, such as from 2 to 7 weight percent, of the totalweight of the 1K structural adhesive composition.

As noted above, in certain embodiments, the 1K structural adhesivecomposition may also include (e) rubber particles having a core/shellstructure. Suitable core shell rubber particles for use in the 1Kstructural adhesives are the same as those described above with respectto the 2K adhesive formulations and therefore not repeated herein.

In certain embodiments, the 1K structural adhesive may include from 0 to75 weight percent, such as from 5 to 60 weight percent, of (e) therubber particles having a core/shell structure, based on the totalweight of the 1K structural adhesive composition.

As noted above, in certain embodiments, the 1K structural adhesivecomposition may also include (f) graphenic carbon particles. Suitablegraphenic carbon particles for use in the 1K structural adhesives arethe same as those described above with respect to the 2K adhesiveformulations and therefore not repeated herein.

In certain embodiments, the 1K structural adhesive may include from 0 to40 weight percent, such as from 0.5 to 25 weight percent, of (f) thegraphenic carbon particles, based on the total weight of the 1Kstructural adhesive composition.

In still other embodiments, the 1K structural adhesive formulation mayalso include epoxy compounds or resins that are not incorporated into orreacted as a part of any of the components (a)-(f) above, includingepoxy-functional polymers that can be saturated or unsaturated, cyclicor acyclic, aliphatic, alicyclic, aromatic or heterocyclic. Theepoxy-functional polymers can have pendant or terminal hydroxyl groups,if desired. They can contain substituents such as halogen, hydroxyl, andether groups. A useful class of these materials includes polyepoxidescomprising epoxy polyethers obtained by reacting an epihalohydrin (suchas epichlorohydrin or epibromohydrin) with a di- or polyhydric alcoholin the presence of an alkali. Suitable polyhydric alcohols includepolyphenols such as resorcinol; catechol; hydroquinone;bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Frequently used polyepoxides include polyglycidyl ethers of Bisphenol A,such as Epon® 828 epoxy resin which is commercially available fromHexion Specialty Chemicals, Inc and having a number average molecularweight of about 400 and an epoxy equivalent weight of about 185-192.Other useful polyepoxides include polyglycidyl ethers of otherpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, epoxy novolac resins, and polyepoxidesthat are partially defunctionalized by carboxylic acids, alcohol, water,phenols, mercaptans or other active hydrogen-containing compounds togive hydroxyl-containing polymers.

In still another embodiment, reinforcement fillers may be added to theadhesive composition. Useful reinforcement fillers that may beintroduced to the adhesive composition to provide improved mechanicalproperties include fibrous materials such as fiberglass, fibroustitanium dioxide, whisker type calcium carbonate (aragonite), and carbonfiber (which includes graphite and carbon nanotubes). In addition, fiberglass ground to 5 microns or wider and to 50 microns or longer may alsoprovide additional tensile strength. More preferably, fiber glass groundto 5 microns or wider and to 100-300 microns in length is utilized.Preferably, such reinforcement fillers, if utilized, comprise from 0.5to 25 weight percent of the 1k adhesive composition.

In still another embodiment, fillers, thixotropes, colorants, tints andother materials may be added to the 1K adhesive composition.

Useful thixotropes that may be used include untreated fumed silica andtreated fumed silica, Castor wax, clay, and organo clay. In addition,fibers such as synthetic fibers like Aramid® fiber and Kevlar® fiber,acrylic fibers, and engineered cellulose fiber may also be utilized.

Useful colorants or tints may include red iron pigment, titaniumdioxide, calcium carbonate, and phthalocyanine blue.

Useful fillers that may be used in conjunction with thixotropes mayinclude inorganic fillers such as inorganic clay or silica.

Exemplary other materials that may be utilized include, for example,calcium oxide and carbon black.

Illustrating the invention are the following examples that are not to beconsidered as limiting the invention to their details. All parts andpercentages in the examples, as well as throughout the specification,are by weight unless otherwise indicated.

EXAMPLES Example 1 2K Adhesive Compositions

Part A—Synthesis of Polyether-Polyester Modified Epoxy Resin

To a four-neck flask fitted with condenser, thermometer, stirrer, andnitrogen inlet, add 304.6 grams of hexahydrophthalic anhydride and 248.1grams of Terathane® 250. Heat the mixture to 100° C. with stirring undernitrogen atmosphere and hold the reaction mixture at 100° C. for 155minutes. Cool the reaction mixture to 60° C. and then add 1431.6 gramsof Epon® 828 and 15.0 grams of triphenyl phosphine. Heat the reactionmixture to 110° C. and hold at this temperature for 150 minutes. Then,cool the mixture to room temperature. The resultant compound has 99.89%solids, an acid value of 0.2, and an epoxy equivalent weight of 380.7.The resultant compound is the epoxy adduct of the first component of the2K adhesive material listed in Part 1 of Table 1 below.

Part B—Evaluation of 2K Adhesives with and without Epoxy-adduct;Evaluation of 2K Adhesives with Varying Amine Hydroxyl EquivalentWeights

The following examples compare 2K adhesive compositions without anepoxy-adduct (Example 1) to those with an epoxy-adduct (Examples 2-4).The formulations for the first component (Part 1) and second component(Part 2) of the 2K adhesive compositions are shown in Table 1.

TABLE 1 Formula Ex. 1 Ex. 2 Ex. 3 Ex. 4 Part 1 Epon ® 828¹ 46 41 40.5 43Epon ® 828/ — 12 12 6 Terathane 250/HHPA² Microglass 6 2 — 4 9132³Hakuenka — — — 1.5 CCR-S⁴ Wacker HDK 3.5 3.25 3.5 3 H17 ⁵ Tint AYD ST0.02 0.02 0.02 0.01 8454⁶ Part 2 Jeffamine D- 11.5 12 12 11.6 230⁷Jeffamine XTJ- 5 5 — 2.5 616⁸ Triethylene- — — 2.3 — tetramine (TETA)⁹IPDA¹⁰ — — — 1.35 Accelerator 2.2 2.2 2.2 0.5 399¹¹ Microglass 1.5 6 8 49132³ Hakuenka 1 1.5 6 2 CCR-S⁴ Wacker HDK 2.75 2.5 2 2.5 H17 ⁵ Tint AYDPC 0.01 0.01 0.01 0.01 9298¹² Results Amine/Epoxy 1.030 1.032 1.0331.036 Ratio Lap Shear 24.5 26.7 25.5 31.4 Strength (MPa) Elongation (%)3.5 3.4 3.7 3.5 Tensile 65 61 68 55 Strength (MPa) Modulus (MPa) 31853127 3473 2931 (data range) (3025-3300) (2974-3274) (3233-3671)(2733-3218) Fatigue Test (8 MPa Stress) cycles to fail 173532 >432000337062 329371 cycles to fail 219062 >432000 >432000 >432000 Average196297 >432000 337062 329371 ¹Bisphenol A/Epichlorohydrin resinavailable from Huntsman Advance Materials ²Synthesis example fromExample 1, Part A ³Silane treated chopped fiberglass from Fibertec⁴Precipitated Calcium Carbonate available from Shiraishi Kogyo Kaisha ⁵Hydrophobic Fumed Silica available from Wacker Chemie AG ⁶ORG YellowTint Base available from Elementis Specialties ⁷Polyoxyalkyleneamineavailable from Huntsman ⁸Polyoxyalkyleneamine available from Huntsman⁹Triethylenetetramine available from Dow Chemical Co. ¹⁰IsophoroneDiamine available from Evonik AG ¹¹Mix of Alkanolamine/piperazinederivative available from Huntsman ¹²Phthlalo Blue Pigment Dispersionavailable from Elementis Specialties

Test Methods

In each of the Examples, the raw materials listed in Table 1 were mixedusing a Speedmixer DAC 600 FVZ (commercially available from FlackTek,Inc.). Ingredients 1 and 2 were mixed for 2 minutes at 2350 revolutionsper minute (“RPM”) in Part 1. Then, items 3 to 6 were added and mixedfor one minute at 2350 RPM. Items 7 to 11 were mixed for 1 minute inPart 2 and then the rest of the ingredients were added and mixed for oneminute in Part 2. During the mixing process, the mixture was examinedwith a spatula and given additional mix time, if necessary, to ensureuniformity. The final step of the mixing process involved mixing themixture with an air motor prop in a vacuum sealed apparatus for 5minutes at 28 to 30 inches of vacuum pressure. After the final mixingstep with the air motor prop, the adhesive compositions were ready fortesting.

Part 1 and Part 2 were targeted for 2:1 volume mix ratio. In someinstances, appropriate weight ratios were determined to test properties.Amine to epoxy ratio were kept slightly over one for all the examples toinsure complete reaction of epoxy as shown in the result section ofTable 1. Appropriate weight ratio of Part 1 and Part 2 were weighed andmixed in the DAC mixer for one minute at 2350 RPM and immediately mixedunder vacuum as described in previous paragraph. The mixed sample wasthen subjected to the following tests:

Lap-Shear Testing: 25 mm×100 mm Coupons were cut from 6-plyunidirectional glass/epoxy laminates supplied by MFG, Inc. with peel plyremoved. Coupons were scribed at one end at 12.5 mm. Adhesive wasapplied evenly on one of the coupons within the scribed area for eachbond assembly. Uniformity of bond thickness is insured by adding 1.0±0.5mm glass spacer beads. Spacer beads were sprinkled evenly over thematerial, covering no more than 5% of the total bond area. The othertest coupon was placed on the bond area and spring loaded clips, such asBinder Clips from Office Max or Mini Spring Clamp from Home Depot, wereattached, one to each side of the bond, to hold the assembly togetherduring bake. Care was given to align parallel edges. Excess adhesivethat was squeezed out was removed with a spatula before baking. Bondassemblies were given an open time of 15 to 30 minutes and baked at 70degrees Celsius for six hours, and after cooling, remaining excess wassanded. Bonds were conditioned at room temperature for at least 24hours. Bonds were inserted in wedge action grips and pulled apart at arate of 10 mm per minute using an Instron model 5567 in tensile mode.Lap Shear strength was calculated by Instron's Blue Hill softwarepackage.

Free film mechanical properties: The same adhesive mix was used toprepare void free dog-bone shaped free film by skiving material withcare to avoid any air pockets. FIG. 1 is an example of a Teflon templateto make five dog-bone cavities. The template was glued to a solid Teflonpiece with double-side adhesive tape prior to skiving adhesive in thecavity. This assembly was given an open air time of 15 to 30 minutes andthen baked at 70° C. for 6 hours. It was conditioned at least 24 hoursand then the dog-bone shaped free film was popped out of the template.Actual thickness and width were recorded into Instron 5567 software.Then, the dog-bone was inserted into the wedge action grip and pulled ata rate of 50 mm per minute. Percent elongation, tensile strength, andmodulus were determined with Instron's Blue Hill software package.Alternatively, ISO 527-1 & 2 method and die configuration was usedwherever indicated in the tables to prepare the dog-bone (dumb-bell)shaped free film.

Load controlled lap-shear fatigue test was done using the same laminateand coupon construction as described in the previous paragraph. Anautomated system utilizing Instron, servo-controlled, hydraulicallyactuated, closed loop test equipment, and a personal computer withsoftware designed by Westmoreland Mechanical Testing and Research, Inc.provided the means for machine control. Each specimen was inserted inwedge action grips along with frictionally retained shims with thicknessequal to that of the fiberglass substrates and bond-line to ensure axialloading. The test was run at room temperature with an R-ratio of 0.1 at5 Hz sinusoidal waveform and load application of 8 MPa. Testing wascontinued until 432,000 cycles or failure.

Part C—Evaluation of Pot Life with 2K Adhesives Having Varying AmineHydroxy Equivalent Weights:

Table 2 shows pot life comparison between propylene oxide-basedpolyether tetramine, Jeffamine XTJ-616, and ethylene oxide-basedtriethylenetetramine in similar formulas, wherein the amine/epoxy ratiowas maintained between 1.03 and 1.05. The formulations and results areshown in Table 2:

TABLE 2 Pot life Comparison Formula Ex. 5 Ex. 6 Part 1 Epon ® 828¹ 4443.5 Epon ® 828/Terathane 250/HHPA² 6 6 Microglass 9132³ 2 1 Wacker HDKH17⁵ 3.5 3 Tint AYD ST 8454⁶ 0.01 0.01 Part 2 Jeffamine D-230⁷ 12 12Jeffamine XTJ-616⁸ 5 Triethylenetetramine (TETA)⁹ — 2.3 Accelerator399¹¹ 0.5 0.5 Microglass 9132³ 5 7 Hakuenka CCR-S⁴ 3 6.64 Wacker HDKH17⁵ 2.25 2.36 Tint AYD PC 9298¹² 0.01 0.01 Amine/Epoxy Ratio (2:1volume mix) 1.033 1.0464 Pot Life, minutes 174 63 Peak Temperature (°C.) 73 150 Minutes to reach Peak 239 83

In this experiment, both formulas (Examples 5 and 6) utilized the sameamount of Accelerator 399 which also has significant influence onpot-life. If Accelerator 399 was absent, the pot life was found to besignificantly higher.

Pot-life was defined as the interval from time when Part 1 (the epoxycomponent) and Part 2 (the amine component) were mixed to the time wheninternal temperature of adhesive reaches 50° C. in 415 ml. of mass. Part1 and Part 2 were mixed in a 2 to 1 volume ratio using a static mixer; PC COX pneumatic dual applicator dispensed mixed adhesive into a papercup marked with 415 ml. level line and initial time was noted. The cupwas immediately placed in 25° C. water bath with a thermo-coupleinserted to the center location of the mixed adhesive mass. PC baseddata logger was employed to record temperature every minute to determinePot-life time taken to reach 50° C., the peak temperature, and the timeto reach the peak temperature.

Part D—Evaluation of 2K Adhesives With and Without Reinforcement Filler

In this experiment, the effect of the addition of fiberglass as areinforcement filler was compared in a sample formulation as describedin Table 3:

Examples 7 and 8 in Table 3 are a comparative study without and withMicroglass 9132 (fiberglass strands with an average of 220 micronlength). Results indicate significant increase in modulus whenMicroglass 9132 is present.

TABLE 3 Effects of Fiberglass on Modulus Properties Formula Ex. 7 Ex. 8Part 1 Epon ® 828¹ 41 41 Epon ® 828/Terathane 12 12 250/HHPA² Microglass9132³ — 6 Wacker HD KH17 ⁵ 3.25 2 Tint AYD ST 8454⁶ 0.02 0.02 Part 2Jeffamine D-230⁷ 12 12 Jeffamine XTJ-616⁸ 5 5 Accelerator 399¹¹ 2.2 2.2Microglass 9132³ — 6 Hakuenka CCR-S⁴ 1.5 1.5 Wacker HDK H17 ⁵ 2.5 2.5Tint AYD PC 9298¹² 0.01 0.01 Amine/Epoxy Ratio 1.032 1.032 Lap ShearStrength (MPa) 27.7 24.4 Elongation (%) 4.8 3.5 Tensile Strength (MPa)66 61 Modulus (MPa) 2444 3211 (data range) (2246-2673) (3160-3269)Part E—Evaluation of 2K Adhesives with Graphenic Carbon Particles;Evaluation of 2K Adhesive Systems with Rubber Particles Having aCore-Shell Structure

The following examples compare 2K adhesive compositions with grapheniccarbon particles (Example 2) or with rubber particles having acore-shellstructure (Example 3). The formulations for the first component (Part 1)and second component (Part 2) of the 2K adhesive compositions are shownin Table 4.

In the example utilizing graphenic carbon particles, twenty grams ofxGnP® Graphene Nanoplatelets (Grade C surface area 750 m²/g (availablefrom XG Sciences Corporation)) was added to pre-weighed Epon® 828 (180grams available from Hexion Specialty Chemicals Corporation) and themixture was hand-mixed with spatula inside a laboratory glove box. Themixture was then poured into a three-roll mill (manufactured by KentIndustrial U.S.A. Inc) and ground 6 times. The graphene ground Epon® 828was poured out from the mill and introduced to the mixture as in Example2 below.

TABLE 4 Formula Ex. 1 Ex. 2 Ex. 3 Part 1 Epon ® 828¹ 41.05 — 38 Epon ®828/Terathane 13 13 5 650/HHPA¹³ 10% Graphenic carbon — 45.61 —particles in Epon ® 828¹⁴ Kane Ace MX-153¹⁵ — — 9 Part 2 JeffamineD-230⁵ 10.35 10.35 10.35 Jeffamine D-400¹⁶ 4.46 4.46 4.46 JeffamineXTJ-616⁸ 2.92 2.92 2.92 IPDA¹⁰ 2.92 2.92 2.92 1,3-Bis(aminometh- 1.041.04 1.04 yl)cyclohexane¹⁷ Triethylenetetramine 0.1 0.1 0.1 (TETA)⁹Accelerator 399¹¹ 0.08 0.08 0.08 Tint AYD PC 9298¹² 0.01 0.01 0.01Results Amine/Epoxy Ratio 1.078 1.081 1.085 Adhesive mechanicalproperties measured according to ISO527-1 & 2 Elongation (%) 5.8 4.8 4.5Tensile Strength (MPa) 55.1 53.6 50.3 Modulus (MPa) 2663 4041 2616 (datarange) (2548-2861) (3571-4505) (2443-2958) ¹³Epon ® 828/Terathane650/Hexahydrophthalic anhydride adduct; EEW 412 ¹⁴Available from XGSciences, Graphenic carbon particles dispersion (10%) in Epon ® 828¹⁵Core-shell poly(butadiene) rubber dispersion (33%) in Epon ® 828available from Kaneka Texas Corporation ¹⁶Polyoxyalkeleneamine availablefrom Huntsman ¹⁷1,3 bis(aminomethyl)cyclohexane (1,3-BAC) available fromMitsubishi Gas Chemical

Example 2 1K Adhesive Compositions

Part A—Synthesis of Polyether-Polyester Modified Epoxy Resin

To a four-neck flask fitted with condenser, thermometer, stirrer, andnitrogen inlet, add 321.3 grams of hexahydrophthalic anhydride and 677.7grams of Terathane® 650. The mixture was heated to 100° C. with stirringunder nitrogen atmosphere and the reaction was checked for an exotherm.After the exotherm subsided, the temperature was set at 150° C. and helduntil the anhydride peak at 1785 and 1855 CM-1 disappeared. The reactionmixture was then cooled to 120° C., wherein 1646.0 grams of EPON 828 and15.0 grams of triphenyl phosphine were added. The reaction mixture washeld at 120° C. until the acid value was below 2.2, resulting in apolyether-polyester modified epoxy resin having an epoxy equivalentweight of 412.

Part B—Synthesis of Polycaprolactone Diol Modified Epoxy Resin

To a suitable flask equipped with a reflux condenser and stirrer, add211.9 grams of hexahydrophthalic anhydride and 570.6 grams ofpolycaprolactone CAPA 2085. The mixture was heated to 100° C. whilestirring and held until the acid value was below 125 and the IRanhydride peaks at 1785 to 1855 CM-1 disappeared. The reaction mixturewas then cooled to ambient temperature and 221 grams of this derivativewas added into another flask equipped with a reflux condenser andstirrer. 310.6 grams of Epon® 828 (bisphenol A epichlorohydrin) and 3.00grams of triphenylphosphine was added to the derivative, and the mixturewas heated to 110° C. while stirring. The heating mantle was removedwhen the exotherm temperature peaked at about 145° C. to allowtemperature to drop. The reaction temperature was then maintained atabout 110° C. until the acid value of the mixture was below 2. Thereaction mixture was then cooled to ambient temperature and stored. Thepolycaprolactone diol modified epoxy resin that resulted had a MolecularWeight by Number Average (M_(n)) of 2042 and an Epoxy Equivalent Weight(EEW) of 435.

Part C—Synthesis of Amide-Polyether-Polyester Modified Epoxy Resin

323.5 grams of Jeffamine D400 and 167.6 grams of E-caprolactone wasadded to a suitable flask equipped with a reflux condenser and stirrer.The mixture was heated to 150° C. while stirring until the MEQ aminevalue was below 0.75 MEQ/gm. The mixture was then cooled to 60° C.,wherein 226.5 grams of hexahydrophthalic anhydride was added to themixture while stirring. The mixture was then heated to 100° C. and helduntil the acid value was below 103. The mixture was then cooled to 60°C., wherein 1061.8 grams of Epon® 828 and 3.7 grams ofTriphenylphosphine were added. The mixture was then heated to 110° C.while stirring and held at that temperature until the acid value wasbelow 2. The mixture was then cooled to ambient temperature and stored.The resultant amide-polyether-polyester modified epoxy resin had aMolecular Weight by Number Average of 1664 and an epoxy equivalentweight (EEW) was 408.6.

Part D—Synthesis of Epoxy/Dimer Acid Adduct

Empol® 1022 Dimer acid (26.95 grams, available from Emory), Epon® 828(32.96 grams available from Hexion) and triphenylphosphine (0.06 gramavailable from BASF) were added in a round-bottom flask, which wasequipped with a mechanical stirrer, a reflux condenser. A thermometerand an addition funnel were attached. Nitrogen gas was brieflyintroduced into the flask. The flask was heated to 105° C. and thereaction continued until the acid value reached the desired rangebetween 85 to 88 mg KOH per gram. An additional amount of Epon® 828(40.03 grams) was added to the flask through a funnel at 105° C. andnitrogen gas was briefly introduced inside the flask. The flask washeated to 116° C. A mild exothermic reaction took place and the reactiontemperature rose to 177° C. The flask temperature was returned to andkept under 168° C. by cooling. The reaction continued until the acidvalue became less than 1, wherein the flask was cooled to roomtemperature. This synthesis made a 43.6% epoxy/dimer acid adductdispersed in an epoxy resin having an Epoxy Equivalent Weight (EEW) of338.6.

Part E—Synthesis of Epoxy/CTBN Adduct

HYCAR 1300X8 carboxylic acid-terminated butadiene—acrylonitrile rubber(40 grams, available from Emerald Performance Materials Corporation) andEpon® 828 (60 grams) were added to a round-bottom flask, equipped with amechanical stirrer, a thermometer and a reflux condenser. The flask waswarmed to 115° C. under a nitrogen atmosphere. The mixture as thenheated to 165° C. and stirred at that temperature until the acid valuebecame less than 0.1, wherein the flask was cooled to room temperature.This synthesis made a 43.9% epoxy/CTBN adduct dispersed in an epoxyresin having an Epoxy Equivalent Weight (EEW) of 357.

Part F—Synthesis of Polyetheramine Modified Epoxy Resin

187 grams of Epon 828 was added to a pint metal can and heated in a 95°C. oven for 30 minutes. The can was removed from the oven and was fittedwith an air-motor driven mechanical stirrer with cowls blade for highshear mixing. 38.33 grams of Jeffamine D-400 was gradually added to thecan under high speed mixing, and the mixture was stirred for threehours. During this period, the temperature of the mixture, initially atabout 120° C. (as measured by a thermocouple), was gradually decreased.After three hours, the can was cooled to room temperature. Thissynthesis made a polyetheramine modified epoxy resin.

Part G—Evaluation of 1K Adhesives

Test Methods

All the mechanical properties were tested on 1 mm thick Hot dipgalvanized (HDG) substrate as supplied by Hövelmann & Lueg GmbH,Germany. Curing conditions for all the testing was 177° C. (350° F.) for30 minutes.

An extension to the ISO 11343 method for wedge impact,“Adhesives—Determination of dynamic resistance to cleavage of highstrength adhesive bonds under impact conditions—Wedge impact method” wasused as described in Ford test method BU121-01. Three bond specimenswere prepared for each testing condition

Wedge Impact Bond Preparation: Cut 90 mm×20 mm coupons. Place Teflon™□tape around the coupons (both the upper and lower coupons) 30.0±□0.2 mmfrom one end. Then apply the adhesive to the top 30 mm. The bond-linethickness is maintained with 0.25 mm (10 mil) glass beads. Removeadhesive squeeze out from the specimen edges with a spatula. Clampspecimens together to maintain flushness of coupon ends and sides. Bondassemblies are cured at 350° F. (177° C.) for 30 minutes. Then removeany excess adhesive from the edges by sanding and ensuring a flat andparallel impact end allowing hammer to impact the entire specimensimultaneously. Mark coupons 40.0±□0.2 mm from the bonded end as alocator for consistent placement on wedge. Place specimen on wedge,aligning mark on specimen with tip of wedge such that it is at the sameplace on the wedge each time. Do not prebend the specimens; however,allow the unbonded portion of the specimens to conform to the shape ofthe wedge as the specimens are placed on the wedge. An Instron DynatupModel 8200 Impact Test frame in conjunction with an integrated softwarepackage provided the means for load application and data acquisitionrespectively. The test frame was set-up with the objective of obtaininga minimum impact energy of 150 joules (110.634 lbf*ft) and an impactspeed of at least 2 meters/second (6.562 ft./sec).

Bonds were conditioned at room temperature for at least 24 hours. Bondswere pulled apart using an Instron model 5567 in tensile mode.

Lap-Shear Testing: 25 mm×100 mm Coupons were cut and scribed at one endat 12.5 mm. Adhesive was applied evenly on one of the coupons within thescribed area for each bond assembly. Uniformity of bond thickness isinsured by adding 0.25 mm (10 mil) glass spacer beads. Spacer beadsshould be sprinkled evenly over the material, covering no more than 5%of the total bond area. The other test coupon is placed on the bond areaand spring loaded clips , such as Binder Clips from Office Max or MiniSpring Clamp from Home Depot, are attached, one to each side of thebond, to hold the assembly together during bake. Excess squeeze out isremoved with a spatula before baking. Bond assemblies were cured asspecified, and after cooling, remaining excess was sanded. Bonds wereconditioned at room temperature for at least 24 hours. Bonds were pulledapart using an Instron model 5567 in tensile mode.

T-peel: Cut metal substrate in pairs of 25 mm×87.5 mm in dimension. Makea 90° bend at 12.5 mm from one end on a vise so that paired pieces makeT-shape configuration: ┐┌ when bonded together. Apply a thin layer ofadhesive on the three inch portion of bonding side of one piece. Apply0.25 mm diameter glass spacer beads evenly over the total bond areamaking sure to cover 5% of total bond area. Place two pieces togetherforming a T-shaped configuration known as T-PEEL assembly. Place 3medium binder clips on the T-PEEL assembly to hold it together. Removeexcess squeeze out of adhesive with a spatula prior to baking theassemblies in a preconditioned oven at a given temperature specified.Allow samples to cool, then remove binder clips, and sand any remainingexcess squeeze out. Pull samples on INSTRON 5567 at rate of 127 mm perminute. T-Peel assemblies in Instron jaws are conditioned in anenvironmental chamber for at least 30 minutes and tested within thechamber in case of −30° C. testing. Instron 5567 calculates results inpounds per linear inch or Newton per mm through internal computerprogram.

Evaluation of 1K Adhesive Compositions With Various Epoxy-CappedFlexibilizers and Rubber Particles Having a Core/Shell Structure

The following examples compare 1K adhesive compositions in accordancewith certain embodiments of the present invention. The formulations areshown in Table 5 and the mechanical performance of the 1K adhesivecompositions is shown in Tables 6-9, respectively.

TABLE 5 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Epon 828/Dimer Acid¹⁸ 4 12 4 4 4Epon 828/CTBN¹⁹ 12 16 12 12 12 Kane Ace MX-153²⁰ 37.5 21 37.5 37.5 37.5Epon 828¹ — 6.5 — — — Epon 828/Terathane 650/HHPA²¹ 10 10 — — — Epon828/Jeffamine D-400²² — — 10 — — Epon 828/Caprolactone/HHPA²³ — — — 10 —Epon 828/Caprolactone/Jeffamine — — — — 10 D-400/HHPA²⁴ Dicyandiamide²⁵5.1 5.1 5.1 5.1 5.1 Diuron²⁶ 0.35 0.35 0.35 0.35 0.35 Raven 410 CarbonBlack²⁷ 0.06 0.06 0.06 0.06 0.06 Calcium Oxide²⁸ 3.1 3.1 3.1 3.1 3.1Wacker HDK H17²⁹ 2.75 3.25 2.5 2.75 2.5 ¹⁸Synthesis example from Example2, Part D above. ¹⁹Synthesis example from Example 2, Part E above.²⁰Core/shell poly(butadiene) rubber dispersion (33%) in Epon ® 828available from Kaneka Texas Corporation. ²¹Synthesis example fromExample 2, Part A above. ²²Synthesis example from Example 2, Part Fabove. ²³Synthesis example from Example 2, Part B above. ²⁴Synthesisexample from Example 2, Part C above. ²⁵Heat activated latent curingagent available from ALZ Chem. ²⁶Catalytically-active substituted ureaavailable from ALZ Chem ²⁷Carbon black available from Phelps Dodge -Columbian Chemicals ²⁸Calcium oxide available from Mississippi Lime, Co.²⁹Hydrophobic Fumed Silica available from Wacker Chemie AG

TABLE 6 Adhesive mechanical properties measured according to ISO527-1 &2 Temp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Elongation (%) Room 10.3 6.0 — — —Pull Rate - 1 mm/min. Temp (RT) Tensile Strength RT 42 38 — — — (MPa)Pull Rate - 1 mm/min. Modulus (MPa) RT 2559 2421 — — — Pull Rate - 1mm/min.

TABLE 7 Lap Shear Strength (MPA) Temp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Bond area - −40° C. 31.4 28.4 29.1 28.4 29.6 25 × 10 × 0.2 mm GM -SAEJ1523 RT 25.3 24.5 23.5 24.9 25.8 Pull Rate - 10 mm/min. +80° C. 22.220.3 21.9 20.7 21.6

TABLE 8 T-Peel Strength (N/mm) Temp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Bondarea - −40° C. 17.6 13.8 17.2 16.2 15.1 25 × 75 × 0.2 mm GM - ASTM D1876RT 15.3 9.3 10.5 10.6 16.4 Pull Rate - 127 mm/min. +80° C. 9.0 8.3 6.58.0 8.7

TABLE 9 Impact Peel Ex. Ex. Ex. Strength (N/mm) Temp. Ex. 1 Ex. 2 3 4 5Bond area - −40° C. 5.8-9.8 3.4-9.4 — — — 25 × 30 × 0.2 mm ISO 11343modified RT 36.9-41.3 29.1-35.1 — — — Ford BU-12-01 +80° C. 31.3-36.933.5-42.9 — — — (2 m/s speed, 150 joules impact energy)

Example 3 1K Adhesive Compositions Containing Epoxy Amine or EpoxyImidazole Catalysts

The following examples compare 1K adhesive compositions with varioustypes of epoxy-amine or epoxy-imidazole catalysts (Example 1-4) and theeffects of a chelating agent (Example 4).

TABLE 10* Example 1 Example 2 Example 3 Example 4 Kane Ace MX-153³⁰ 4848 48 48 Epon 828/Terathane 13.4 13.4 13.4 13.4 650/HHPA³¹ Epon828/Dimer 5 5 5 5 Acid Adduct³² 1,10-Phenanthroline³⁴ — — — 1 TTNT-AYDST 8703³⁶ — — 0.1 0.1 Raven 410³⁷ 0.06 0.06 — — Mica A-325³⁸ 3.3 3.3 1 1Calcium Oxide³⁹ 3.1 3.1 2 2 HDK H17⁴⁰ 1.1 1.1 1.1 1.1 Dyhard 100SF⁴¹ 6.86.8 3.4 3.4 Ajicure MY-25⁴² — — — 1.5 Ajicure PN-40⁴³ 1.5 — 2 1.5Ajicure PN-50⁴⁴ — 1.5 — — Diuron⁴⁶ — — — 0.3 Bake: 130° C. metaltemperature for 10 minutes Lap shear strength (MPa) HDG metal - 1 mmthick: Bond area: 20 mm × 10 mm × 0.25 mm Room Temperature 18.5 18.417.7 15.6 Water Soak, 54° C./7 days, 24 hrs dry Lap shear strength (MPa)11.6 12.7 11.6 11.7 T-Peel strength (N/mm) HDG metal - 0.7 mm thick:Bond area: 20 mm × 70 mm × 0.25 mm Room Temperature 9.0 5.6 4.3 7.6 EZGmetal - 0.7 mm thick: Bond area: 20 mm × 70 mm × 0.25 mm RoomTemperature 6.3 3.8 4.1 8.2

The following examples compare adhesive compositions with varyingcombinations of epoxy resins.

TABLE 11* Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10Kane Ace MX-153³⁰ 48 48 53.12 53 48 48 48 48 48 48 Epon 828/Terathane650/HHPA³¹ 13.4 13.4 13.28 13.4 13.4 13.4 9.9 10.4 18.4 13.4 Epon828/Dimer Acid Adduct³² — 5 — — 1.5 1.5 5 8 — 1.5 Epon 828/CTBN Adduct³³5 — — — 3.5 3.5 3.5 — — 3.5 1,10-Phenanthroline³⁴ — — — 1 — — 0.4 0.40.4 0.4 Halox SW 111³⁵ — — — — — — 0.4 0.4 0.4 0.4 TINT-AYD ST 8703³⁶0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Mica A-325³⁸ 1 1 1 1 1 — 1 1 1 1Calcium Oxide³⁹ 2 2 2 2 2 2 2 2 2 2 HDK H17⁴⁰ 1.1 1.1 1.1 1.1 1.1 — 1.11.1 1.1 1.1 Dyhard 100SF⁴¹ 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4Ajicure MY-25⁴² 0.5 0.5 — — 0.5 0.5 0.5 0.5 0.5 — Ajicure PN-40⁴³ 1.51.5 2 2 1.5 1.5 1.5 1.5 1.5 1.5 Technicure PPG-1⁴⁵ — — — — — — — — — 1Diuron⁴⁶ 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Bake: 130° C. metaltemperature for 10 minutes Lap shear strength (MPa) HDG metal - 1 mmthick; Bond area: 20 mm × 10 mm × 0.25 mm Room Temperature 14.6 14.519.3 17.9 20.0 12.0 17.9 18.4 21.0 18.3 Water Soak, 54° C./7 days, 24hrs dry Lap shear strength (MPa) 10.8 10.3 9.8 13.1 13.5 — 13.6 12.614.2 13.8 T-Peel strength (N/mm) HDG metal - 0.7 mm thick; Bond area: 20mm × 70 mm × 0.25 mm Room Temperature 5.4 5.8 2.8 1.7 7.0 4.9 1.3 2.03.5 3.6 EZG metal - 0.7 mm thick; Bond area: 20 mm × 70 mm × 0.25 mmRoom Temperature 3.5 6 6.6 3.7 6.1 3.4 5.1 5.5 6.1 7.9 *List ofIngredients for Tables 10 and 11. ³⁰Kane Ace MX-153: Core-shell rubberdispersion in Epon 828 epoxy resin available from Kaneka Corporation.³¹Epon 828/Terathane 650/HHPA: Synthesis example from Example 2, Part Aabove. ³²Epon 828/Dimer Acid: Synthesis example from Example 2, Part Dabove. ³³Epon 828/CTBN: Synthesis example from Example 2, Part E above.³⁴1,10-Phenanthroline: A chelating agent available from AldrichChemical. ³⁵Halox SW 111: Calcium Strontium phosphosilicate availablefrom Halox Pigments. ³⁶Tint-Ayd ST 8703: Organic dye available fromElement Specialties, Inc. ³⁷Raven 410: Carbon black powder availablefrom Columbian Chemicals Canada. ³⁸Mica A-325: Silicate mineralavailable from Franklin Industrial Minerals. ³⁹Calcium oxide:Mississippi Lime Company. ⁴⁰HDK H17: Fumed silica available from WackerChemie ⁴¹Dyhard 100SF: Dicyanamide powder available from Alz Chem.⁴²Ajicure MY-25: Epoxy-amine adduct available from A & C Catalysts.⁴³Ajicure PN-40: Epoxy-imidazole adduct available from A & C Catalysts⁴⁴Ajicure PN-50: Epoxy-imidazole adduct available from A & C Catalysts⁴⁵Technicure PPG-1: Encapsulated epoxy latent catalyst available from A& C Catalysts. ⁴⁶Diuron: Modified urea available from Alz Chem.

Test Methods

Lap shear properties were tested on 1 mm thick hot dip galvanized (HDG)steel substrate as supplied by Hövelmann & Lueg GmbH, Germany. T-peelproperties were tested on 0.7 mm thick hot dip galvanized andelectogalvanized (EZG) steel panels as supplied by ACT Test Panels.Curing conditions for all the testing was 130° C. (266° F.) metaltemperature for 10 minutes.

Lap-Shear Testing: 20 mm×90 mm coupons were cut and scribed at one endat 10 mm. Adhesive was applied evenly on one of the coupons within thescribed area for each bond assembly. Uniformity of bond thickness wasinsured by adding 0.25 mm (10 mil) glass spacer beads. Spacer beads weresprinkled evenly over the material to cover no more than 5% of the totalbond area. The other test coupon was placed on the bond area and springloaded clips, such as Binder Clips from Office Max or Mini Spring Clampfrom Home Depot, were attached, one to each side of the bond, to holdthe assembly together during bake. Excess squeeze out was removed with aspatula before baking. Bond assemblies were cured as specified, andafter cooling, remaining excess was sanded. Bonds were conditioned atroom temperature for at least 24 hours. Bonds were pulled apart using anInstron model 5567 in tensile mode.

Water soak: Assemblies prepared in the same manner as those forlap-shear testing were made and placed in a 54° C. water tank for 7days. After removing the assemblies from the water tank at the end of 7days, the assemblies were dried for 24 hours before testing. The testspecimens were pulled with Instron mode 5567 using the same lap-sheartest method as described above.

T-peel: Metal substrate was cut in pairs of 1 inch×4 inch in dimension.A 90° bend was at 0.5 inch from one end on a vise so that paired piecesmade a T-shaped configuration: ┐┌, when bonded together. A thin layer ofadhesive was applied on the unbent portion of bonding side of one piece.A 0.25 mm diameter glass spacer beads were applied evenly over the totalbond area to cover 5% of total bond area. Two pieces were placedtogether to form a T-shaped configuration known as T-PEEL assembly. Twolarge binder clips were placed on each side of the T-PEEL assembly tohold it together. Excess squeeze out of adhesive was removed with aspatula prior to baking the assemblies in a preconditioned oven at aspecified temperature. The samples were cooled, the binder clips wereremoved, and any remaining excess squeeze out was sanded. Samples werepulled on INSTRON 5567 at rate of 50 mm per minute. Instron 5567calculated results in Newton per mm through an internal computerprogram.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

We claim:
 1. A one-component composition comprising: (a) 2% by weight to40% by weight, based on total weight of the one-component composition,of an epoxy-capped flexibilizer comprising a reaction product ofreactants comprising (i) an epoxy compound, (ii) an anhydride and/or adiacid, and (iii) a caprolactone; (b) 3% by weight to 25% by weight,based on total weight of the one-component composition, of aheat-activated latent curing agent comprising dicyandiamide having a D98maximum of 6 μm and a reaction product of reactants comprising an epoxycompound and an imidazole, wherein the epoxy compound comprises apolyepoxide and the molar ratio of the epoxy compound to the imidazoleis 1:1 to 3:1; (c) 5% by weight to 60% by weight, based on total weightof the one-component composition, of rubber particles having acore/shell structure and dispersed in an epoxy carrier resin; and (d) 1%by weight to 15% by weight, based on total weight of the one-componentcomposition, of an adduct of an epoxy compound and a dimer acid.
 2. Thecomposition of claim 1, wherein the epoxy compound reactant (i)comprises Bisphenol A diglycidyl ether, phenyl diglycidyl ether, orcombinations thereof.
 3. The composition of claim 1 further comprisinggraphenic carbon particles, an epoxy/CTBN adduct or a combinationthereof.
 4. The composition of claim 1, wherein the heat-activatedlatent curing agent (b) further comprises3,4-dichlorophenyl-N,N-dimethyl urea.
 5. The composition of claim 1,wherein the composition is curable at a temperature below 140° C.
 6. Thecomposition of claim 1, wherein the composition is heat-curable within15 minutes or less.
 7. The composition of claim 1, wherein thecomposition is heat-curable within 15 minutes or less at a temperatureof below 140° C.
 8. The composition of claim 1, which, when applied at 1mm thick to hot dipped galvanized metal with a bond area of 20 mm×10mm×0.25 mm, and following heating, has a measured lap shear strength ofat least 15 MPa when tested at room temperature.
 9. A method of adheringarticles comprising: (a) applying the composition of claim 1 to at leastone of the articles; and (b) heating the composition at a temperature ofless than 140° C. for a time of less than 15 minutes to cure thecomposition and thereby adhering the articles together.